Record per-site probe provenance in completed fixtures (#168)

Spec review flagged the live-verification acceptance criterion as
unproven in the diff: the brief's adapter rule wants the probe
recorded, not just the date. Each fixture comment now names how the
live body was fetched on 2026-08-22 — curl probe for asura,
demonic and lightnovelworld; cleared Chrome tab (CDP sidecar) for
comix, kagane and novelfull, including the challenge/403 fallback
story for novelfull. Also renamed lnwCompletedRe to lnwStatusRe for
symmetry with the other site-marker vars.

backend/internal/latest/sites.go

@@ -437,10 +437,10 @@ func novelfullCompleted(_, body string) bool {
 // whole body is scanned and the comment marker is not required, unlike
 // lnwLatestChapter: the status block sits ahead of the visitor-writable
 // thread, and hiatus maps to a distinct PotentialActionStatus value.
-var lnwCompletedRe = regexp.MustCompile(`"creativeWorkStatus"\s*:\s*"https://schema\.org/CompletedActionStatus"`)
+var lnwStatusRe = regexp.MustCompile(`"creativeWorkStatus"\s*:\s*"https://schema\.org/CompletedActionStatus"`)
 
 func lnwCompleted(_, body string) bool {
-	return lnwCompletedRe.MatchString(body)
+	return lnwStatusRe.MatchString(body)
 }
 
 // siteCompletedFrom reports whether the Site calls this work completed, via